class_docstr: Base Data Geneartor
code: def __init__(self, buf_size, batch_size, num_workers, shuffle=True):
      self.num_workers = num_workers
      self.batch_size = batch_size
      self.line_examples = []
      self.buf_size = buf_size
      self.shuffle = shuffle
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  from __future__ import absolute_import
  import os
  import sys
  import six
  from io import open
  from collections import namedtuple
  import numpy
  import tqdm
  import paddle
  from pgl.utils import mp_reader
  import collections
  import time
  from pgl.utils.logger import log
  import traceback
label_desc: Use image node_id 1 to create a new BaseDataGenerator object from inherited base classes: object with example: obj = BaseDataGenerator(buf_size, batch_size, num_workers, shuffle)